Sweep sounded out bottom of flue (5)
I believe the answer is:
range
'sweep' is the definition.
(both can mean extent or variety)
'sounded out bottom of flue' is the wordplay.
'sounded' becomes 'rang' (ringing is a kind of sounding).
'out bottom of flue' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'rang'+'e'='RANGE'
Can you help me to learn more?
(Other definitions for range that I've seen before include "Number of items in a series" , "Aga or mountain, perhaps?" , "Distance between weapon and target" , "Sierra" , "Scope; ambit" .)